Local relapse can occur for several reasons. One primary cause is the presence of microscopic cancer cells that remain after surgery or other treatments, which were not detectable during initial diagnosis and treatment. These residual cells can eventually grow into a new tumor. Another reason could be the resistance of cancer cells to treatment, allowing them to survive and proliferate. Additionally, factors such as tumor biology, incomplete surgical margins, and the inherent characteristics of the cancer type can contribute to local relapse.
